Thermal energy applicator

ABSTRACT

An apparatus and method, for selective thermal treatment of tissue, below the surface, while avoiding injury to the superficial layers of the tissue. The apparatus comprises a reflective beam conversion system for providing a pre-selected therapeutic dose of light energy of optimal spectrum and optimal pulse duration to a confined target volumes at predetermined depth under the tissue surface, while reducing the thermal exposure of the surface of the tissue, and the overlying and surrounding tissues. The method is advantageous for treating a variety of medical and dermatological conditions in a safer and more effective manner.

FIELD OF THE INVENTION

The present invention relates to the field of the application of lightenergy for thermal treatment below the surface of tissue, while reducingthe risk of damage to the surface of the tissue, especially as appliedto dermatological thermal treatment.

BACKGROUND OF THE INVENTION

Applying heat is a well-known technique for treating human tissue.Multiple thermal treatment techniques exist for tissue ablation andcoagulation as well as for non-ablative tissue stimulation andregeneration. Those techniques include radio-frequency ablation (RFA),microwave, focused ultrasound and lasers. Lasers, and in some cases,other light sources such as intense pulsed light (IPL) sources areespecially suitable for the delivery of the required thermal dose to thetissue being treated. Laser radiation energy is measured in Joules (J)and is directly proportional to the quantity of photons of theradiation. Power is the rate of energy exposure measured in Watts (W)where 1 W=1 J/s. Power Density, also known as Irradiance refers to theamount of power per area and is expressed in Watts per centimetersquared (W/cm2). The total amount of energy exposed to a surface isknown as the Fluence=Power×Time/Area and is expressed in term of Joulesper centimeter squared (J/cm²). In laser surgery, fluence determines thetotal volume of tissue damage.

In many medical and dermatological applications, the aim of thetreatment is to deliver a predetermined amount of thermal energy to adesired target volume of tissue at a specific depth below the surface,while sparing the adjacent and overlying tissue.

One of the disadvantages of prior art laser techniques is its limitedability to deliver significant energy to a desired depth in the tissue,through superficial layers of the tissue, without exposing thesuperficial layers to significant levels of energy, which can causeundesirable effects to the superficial layers. Moreover, due to tissueattenuation effect, in order for the deeper tissue layers to receivesufficient amount of energy, the superficial layers are exposed to evenhigher levels of energy thus increasing these undesirable side effects.

Optical scanners have been proposed for addressing problems such asvariable depth penetration, non-uniform exposure and consequent charringof tissue surface. In general, prior art scanners, such as thosedescribed in U.S. Pat. No. 5,743,902 to Trost, displace an opticaltreatment beam from one treatment spot to another in a controlledmanner. Other scanners such as those described in U.S. Pat. No.5,582,752 to Zair and U.S. Pat. No. 5,786,924 to Black et al,additionally provide focusing of the beam on the surface usingrefractive optics (such as lenses) or reflective optics (such as concaveand convex mirrors) to provide homogeneous vaporization of the tissue.Although those scanners provide some improvement by allowing moreuniform coverage of the surface, they don't address the problem ofmanaging the desired level of energy delivery below tissue surface.

A known technique to address the problem of selective targeting whilesparing the adjacent tissues is called Selective Photothermolysis (SP),in which selective tissue thermal damage can be achieved using opticalenergy with a wavelength that is specifically absorbed by a natural orartificially introduced chromophore in the target area. In addition, theprocess also involves choosing the duration of the energy pulse tomaximize the temperature of the target before significant diffusion ofheat to the surrounding tissue can take place. This technique, in theprior art, is limited and is applicable only to applications whereby thetreated target has spectral absorption which is different from theadjacent tissue. This isn't the case in many applications.

For example, prior art optical technologies for long-term hair removaltreatment are based on thermal destruction of the hair shaft andfollicle using wavelengths that are specifically absorbed by the pigmentmelanin found in the hair follicle. One of the limitations of thosetechnologies is the fact that the epidermis through which the lightenergy must penetrate is rich in melanin and therefore absorbs a majorportion of the energy, resulting in inadequate heating of the hairfollicles as well as damage to the epidermis. Using higher energy levelsin order to generate sufficient heating of the hair follicles can causecharring and hyper-pigmentation. Although the chromophore being targetedmay vary for different applications, the above limitations are commonfor all such applications.

Another problem with selective photothermolysis is that the wavelengthselected for the radiation is generally dictated by the absorptioncharacteristics of the chromophore utilized. However, such wavelengthsmay not be optimal for penetration deep enough to reach the target dueto tissue scattering which depends on wavelength.

Various techniques have been used or proposed to assist in improving theefficiency of the process. These techniques include pre-cooling of thetreated area, cooling during the process, selective cooling of theepidermis using millisecond cryogen spray, use of optical transmittinggels to improve coupling into the tissue, convex shaped applicators, anddevices to draw folds of skin which may receive radiation from bothsides.

Another approach, described in U.S. Pat. No. 5,735,844 to Anderson etal., in International PCT patent application published as WO 98/52481 toColles and in U.S. patent application Ser. No. 10/033,302 to Anderson etal., use various types of refractive elements such as lenses to focusthe optical energy at specific depth under the skin surface, thusincreasing the energy fluence at the depth. There are severaldisadvantages associated with this approach:

-   -   1. Optical focusing in the tissue substantially increases the        power density of the beam. Such increased power density at a        focal point and its immediate proximity is very difficult to        control, which may create a serious epidermis safety hazard.        This is particularly true with low numerical aperture focusing        systems, easily realizable with refractive optics.    -   2. There can be a significant thermal exposure to overlying        tissue located above the target, especially that in close        proximity to the target region at the focus.    -   3. Inability to simultaneously treat multiple, separate targets        at different depths using different wavelengths and different        light pulse durations.    -   4. Focusing of the beam using lenses, generally requires contact        with the skin surface, which may complicate practical        implementation of this method, for example, by precluding use of        galvanic scanners.

It must be emphasized that focusing techniques may also lack inherentaccuracy and may be dependent on the particular properties of thepatient's skin. Scattering of radiation inside the skin may preclude thepossibility to attain a well defined focus as well as a well definedtreatment depth.

Whereas there may be both advantages and disadvantages to varyingdegrees in all of these approaches, it is clear that there is a need foran improved light energy delivery system that addresses the problems ofsub-surface thermal treatment.

It would therefore be desirable and advantageous to devise an effectivemethod and apparatus for medical and aesthetic thermal treatment oftissue at the desired depth, while minimizing the thermal damage to theoverlying layers of the tissue.

Accordingly, it is an object of the present invention to overcome thedisadvantages of prior art methods and provide an improved method andapparatus for thermal treatment of a tissue. More specifically, it is anobject of the invention to provide an apparatus for thermal treatment ofconfined tissue volumes at predetermined depths, while minimizing thedamage to overlying, superficial tissue layers and surrounding tissues,thus significantly improving the safety of the procedure. Anotherobjective is improving the efficacy of thermal treatment methods bydelivering significantly higher fluence levels to the target, thanachievable with prior art methods, still preserving safe fluence levelat the tissue surface. Another objective is providing an apparatuscapable of treating a variety of medical and dermatological conditions.

The foregoing objectives are attained by the apparatus and method of thepresent invention.

The disclosures of each of the publications mentioned in this sectionand in other sections of the specification, are hereby incorporated byreference, each in its entirety.

SUMMARY OF THE INVENTION

The present invention seeks to provide a system for providing apredetermined therapeutic dose of electromagnetic energy of optimalspectrum and optimal pulse duration to a target volume at apredetermined depth beneath the tissue surface, while reducing thethermal exposure of overlying and surrounding tissues. The systempreferably comprises a controllable radiation source for generating aradiation beam, and a controllable treatment head. The electromagneticenergy preferably comprises a narrow band light source or amonochromatic light source such as a laser. The treatment headpreferably comprises at least one controllable beam conversion system,which is generally reflective in operation.

The tissue is preferably the skin of a subject to be treated, or anotherbody organ having an accessible surface.

In general, the beam conversion system receives the input radiationbeam, of predetermined initial fluence, and is operative to spread itout as it reaches the surface of the tissue thereby reducing the averageenergy fluence on the surface, and at the same time, to recollect thespread-out radiation into beams which cross each other in the targetvolume at a predetermined depth below the tissue surface, thus exposingthe target volume to energy fluence that is substantially higher thanthe average energy fluence on the surface, without increasing the energyfluence at other skin sites. The beam conversion system thus delivers atherapeutic dose to the target volume and can repeat this action for aplurality of target volumes to cover the entire desired treatment area.

It is to be understood that the beam conversion system of the presentinvention does not rely on any optical power to converge the spread outradiation components onto the target volume. The beam converter canoperate on a pure collimated beam, which can maintain a non-convergentcollimated nature as it is spread out, and as the spread out radiationis reassembled. The terms reconverge, reassemble, recombine, recollector similar, as used and claimed in the application, are not mean toimply optical convergence of a beam, such as is accomplished by anelement having optical power, but rather the collection of thespread-out beam components, whether spatially or temporally, such thatthey meet and cross at the target volume. The input, spread out andreassembled or reconcentrated beam components can be opticallyconverged, diverged or collimated, but the beam converter of the presentinvention operates in a manner unrelated to these properties.

According to one preferred embodiment, the beam conversion systemspreads the radiation beam by reducing the radiation exposure time atthe surface while sustaining the radiation exposure time at the targetvolume. This is achieved by diverting the beam away from the axis of theinput beam and then redirecting the beam back inwards towards the inputbeam axis at a predetermined incident angle to the surface, causing thebeam to cross the symmetry axis at the target point, below the surface.The beam is rotated around the axis, thus exposing any given point ofthe target volume to radiation during the entire energy excitationperiod, while any given point of the surface is exposed to radiationonly during a fraction of the energy excitation period, as the rotatingbeam passes over it.

According to a second preferred embodiment, the beam conversion systemspreads out the input radiation beam by increasing the radiationexposure area at the surface while maintaining the radiation exposurearea at the target volume. This is realized by splitting the radiationbeam into a plurality of static beams directed away from the inputoptical axis, and redirecting the plurality of beams inwards, backtowards the axis at predetermined incident angles to the surface, suchthat they reassemble together at a crossing point at a predetermineddepth generally at the target volume.

According to another preferred embodiment, a scanning system is added tothe beam conversion system, allowing combined functionality of both ofthe previous embodiments—the time divided beam embodiment and the spacedivided beam embodiment, as well as improved flexibility in some of theoperating parameters of the system.

Additional uses and functions of the present invention include:

-   -   1. The simultaneous treatment of multiple targets with different        wavelengths and exposure times.    -   2. Reduction of pain by scanning the treatment area in discrete        steps, not adjacent to each other.    -   3. Cooling of the surface of the skin and epidermal tissue above        the targeted dermal region before and/or during the thermal        treatment to minimize injury to the surface of the skin while        irradiating the skin.    -   4. Use of multiple sources of energy such as radiofrequency        (RF), microwave, ultrasound or other electromagnetic radiation        applied simultaneously or sequentially in combination with the        light energy.    -   5. A visible aiming beam that creates a marking spot on the        surface of the skin under which the target point is located.    -   6. A sensing system for determining the speed of rotation of the        beam conversion system and for determining the location of the        light beam impinging on the surface.    -   7. Manual repositioning of the beam conversion system to new        treatment location.    -   8. A plurality of treatment heads, arranged in a two-dimensional        matrix for simultaneous or sequential operation.    -   9. A mechanical, two-dimensional positioning system for scanning        the treatment area.    -   10. An optical tracking system for tracking and controlling the        location of the target zones in the treatment area    -   11. A transparent element applied between the treatment head and        the surface for improved light coupling into the tissue.    -   12. An imaging system for assisting in locating the target.

The method and apparatus of the present invention broadly can be usedfor treating a variety of medical and dermatological conditions such aswrinkles, sagging and folding skin, an excess of unwanted hair, vascularconditions, sub-surface ablation and many other conditions that requirethermal treatment.

The method comprises providing an input beam of radiation preferablyhaving a wavelength between 0.3 and 11 microns, providing at least onecontrollable beam conversion system for spreading out the beam ofradiation such that it impinges on the surface of the tissue overlyingthe target with a larger area than the input beam, thereby reducing theaverage energy fluence on the surface. The method further comprisesreassembling the spread-out beam or beams so that they cross at leastone target volume, at a predetermined depth below the tissue surface,thus exposing the target volume to energy fluence substantially higherthan the average energy fluence on the surface. In one embodiment theresulting fluence at the target is normally no higher than the fluenceof the initially provided beam of radiation. In another embodimentfluence at the target is higher than of the initially provided beam ofradiation as might be required by some applications.

The method further comprises repeating this action for a plurality oftarget volumes consequently or simultaneously, by manually ormechanically repositioning the reflective beam conversion system tocover the desired treatment area. The method further comprises trackingand controlling the location of the target zones in the treatment area.Additionally, the method comprises consequently or simultaneouslytreating multiple vertically separated target volumes with differentwavelengths and exposure times. Furthermore, the method comprisesapplying gel to the skin surface. The method further comprises utilizingan imaging system for assisting in locating the target.

The invention offers numerous advantages over existing medical anddermatologic procedures and devices.

The non-target tissue layers overlying the target tissue remain intact,thereby avoiding undesirable side effects which may arise when usingprior art techniques.

Furthermore, the invention allows the delivery of significantly higherenergy fluence to the target than when using prior art methods, whichcan induce more effective treatment, while still preserving the safetyof the procedure. Moreover, delivering higher energy to the targettissue can achieve the desired thermal effect while requiring much lesschromophore in the target tissue. Consequently, the selection ofradiation wavelength is less restricted by the target chromophore,therefore wavelengths capable of deeper tissue penetration can beutilized thus allowing treatment of deeper targets.

Additionally, because the invention does not require focusing the energyunder the surface, the maximum power density at the target is morecontrollable, resulting in a significantly safer procedure. In addition,the invention does not require refractive optical elements which mayhave a low numerical aperture and consequent increased danger of damageto the epidermis. Moreover, the invention permits considerably moreeffective avoidance of overheating of the overlying tissue, either onthe surface or even under the surface in close proximity to the target.

Still another advantage is the ability to produce target volumes ofdesired shape, size, energy distribution and depth under the surface.Yet another advantage of the invention is the ability to simultaneouslytreat multiple, separate targets at different depths using differentwavelengths and different pulse durations.

The invention allows treatment of a variety of medical anddermatological conditions with a single piece of apparatus, whileseparately optimizing the treatment parameters for each application.

There is thus provided in accordance with a preferred embodiment of thepresent invention, apparatus for delivering radiation beneath a tissuesurface, comprising:

(i) a radiation source for inputting a beam of the radiation ofpredetermined energy fluence, and

(ii) a beam converter having a symmetry axis, the beam converter adaptedto direct the input radiation in a plurality of directions spaced aroundthe symmetry axis and inclined angularly to the symmetry axis, towardsat least one target volume disposed on the symmetry axis beneath thesurface, wherein

the radiation has an energy fluence at the surface which is lower on theaxis than the maximum energy fluence of the radiation on the surface,

the energy fluence of the radiation at the surface is lower than thepredetermined energy fluence of the input beam, and

the energy fluence of the radiation at the at least one target volume ishigher than the energy fluence of the radiation at the surface.

In accordance with yet another preferred embodiment of the presentinvention, there is provided apparatus as described in the previousparagraph, and wherein the beam converter comprises a rotator having arotation axis collinear with the symmetry axis for rotating the inputradiation around the symmetry axis, such that the radiation is spreadout in a rotational path on the surface. Alternatively and preferably,the beam converter further comprises at least one reflective element fordirecting the radiation through the surface radially inwards towards thesymmetry axis and the target volume. The radiation preferably has aspectral band between 300 nm and 11000 nm.

There is further provided in accordance with yet another preferredembodiment of the present invention apparatus as described above, andwherein the energy fluence of the directed input radiation may be lessthan or equal to the predetermined energy fluence. Additionally, theradiation at the target volume may preferably have an energy fluenceless than or equal to the predetermined energy fluence. Furthermore, inany of the above described embodiments, the rotated radiation maypreferably be in a collimated form. Moreover, the distance of the targetvolume beneath the surface may preferably be adjustable.

In accordance with still another preferred embodiment of the presentinvention, there is also provided the above mentioned apparatus fordelivering radiation beneath a tissue surface, but wherein the beamconverter comprises a reflective beam divider for spreading the inputradiation in the plurality of directions, and a reflective beamcollector for redirecting the spread out radiation towards the targetvolume. The radiation preferably has a spectral band between 300 nm and11000 nm, and the energy fluence of the redirected radiation ispreferably less than or equal to the predetermined energy fluence.

In any of the above-described apparatus, the at least one target volumemay preferably be at least two target volumes, and the radiation isdelivered to the at least two target volumes substantiallysimultaneously. In such preferred embodiments of the apparatus of thisinvention, the radiation preferably comprises at least first and secondspectral bands, and the radiation of the at least first spectral band isdelivered to one of the at least two target volumes, and the radiationof the at least second spectral band is delivered to a second one of theat least two target volumes.

There is also provided in accordance with yet another preferredembodiment of the present invention, apparatus for delivering radiationbeneath a tissue surface, comprising:

(i) a radiation source for inputting a beam of the radiation, and

(ii) a beam converter having a symmetry axis, the beam converter adaptedto direct the radiation in a plurality of directions spaced around thesymmetry axis such that the majority of the radiation crosses thesurface remotely from the symmetry axis, and inclined angularly towardsthe symmetry axis. The beam converter may preferably comprise a rotatorhaving a rotation axis collinear with the symmetry axis, for rotatingthe input radiation around the symmetry axis, such that the radiation isspread out in a rotational path on the surface. Alternatively andpreferably, the beam converter may comprise a reflective beam dividerfor spreading out the input radiation in the plurality of directions,and a reflective beam collector for redirecting the spread out radiationtowards the symmetry axis, onto a target volume.

There is further provided in accordance with still another preferredembodiment of the present invention, a method for delivering radiationbeneath a tissue surface, comprising the steps of:

(i) providing a radiation source for inputting a beam of the radiationof predetermined energy fluence, and

(ii) converting the input beam into radiation directed in a plurality ofdirections spaced around a symmetry axis and inclined angularly to thesymmetry axis, towards at least one target volume disposed on thesymmetry axis beneath the surface, such that:

the radiation has an energy fluence at the surface which is lower on theaxis than the maximum energy fluence of the radiation at the surface,

the energy fluence of the radiation at the surface is lower than thepredetermined energy fluence of the input beam, and

the energy fluence of the radiation at the at least one target volume ishigher than the energy fluence of the radiation at the surface.

In accordance with yet another preferred embodiment of the presentinvention, there is provided a method as described in the previousparagraph, and further comprising the step of rotating the inputradiation around the symmetry axis, such that the radiation is spreadout in a rotational path on the surface. This method, according toanother preferred embodiment of the present invention, can also comprisethe step of providing at least one reflective element for directing theradiation through the surface radially inwards towards the symmetry axisand the target volume. The radiation preferably has a spectral bandbetween 300 nm and 11000 nm. Additionally and preferably, the energyfluence of the directed input radiation may be less than or equal to thepredetermined energy fluence. Furthermore, the radiation at the targetvolume may preferably have an energy fluence which is less than or equalto the predetermined energy fluence.

In accordance with further preferred embodiments of the presentinvention, in any of the above described methods, the rotated radiationmay be in a generally collimated form. Furthermore, the distance of thetarget volume beneath the surface may preferably be adjustable.

The above-described method for delivering radiation beneath a tissuesurface may also comprise the step of providing a reflective beamdivider for spreading the input radiation in the plurality ofdirections, and a reflective beam collector for redirecting the spreadout radiation towards the target volume. In such a case, the energyfluence of the directed input radiation may preferably be less than orequal to the predetermined energy fluence, and the radiation maypreferably have a spectral band between 300 nm and 11000 nm.

In any of the above-described methods, the at least one target volumemay preferably be at least two target volumes, and the radiation isdelivered to the at least two target volumes substantiallysimultaneously. In such preferred embodiments of the methods of thisinvention, the radiation preferably comprises at least first and secondspectral bands, and the radiation of the at least first spectral band isdelivered to one of the at least two target volumes, and the radiationof the at least second spectral band is delivered to a second one of theat least two target volumes.

BRIEF DESCRIPTION OF DRAWINGS

The foregoing and other objects, features and advantages of theinvention will become apparent from the following more particulardescription of preferred embodiments of the invention, as illustrated inthe accompanying drawings. The drawings are not necessarily to scale,emphasis instead being placed on illustrating the principles of thepresent invention.

FIG. 1A is a general view the apparatus, including the radiation sourcea delivery system and the treatment head for practicing the invention.

FIG. 1B exemplifies an application of the treatment head on patient'sskin.

FIG. 1C shows a simplified schematic block diagram of the apparatus.

FIG. 2A shows a conceptual illustration of the beam conversion systemincorporating the principles of the invention.

FIG. 2B illustrates one embodiment of the beam conversion systemincorporating the principles of the invention.

FIG. 3A to 3E illustrate a perspective view of different embodiments ofthe beam conversion system incorporating the principles of theinvention. The different embodiments allow creating target volumes ofvarious shapes.

FIG. 3F illustrates another embodiment of the beam conversion systemincorporating the principles of the invention in which the radiationsource is included in the conversion system.

FIG. 3G illustrates another embodiment of the beam conversion system inwhich the radiation source is used without reflecting elements.

FIG. 4A illustrates an interaction between the laser beam and the tissueaccording to the principles of the invention.

FIG. 4B illustrates another embodiment of the interaction between thelaser beam and the tissue according to the principles of the invention.

FIG. 5A shows a perspective view of the light beam projected on thesurface in accordance with the principals of the present invention.

FIG. 5B shows a perspective view of an alternative projection of thelight beam on the surface in accordance with the principals of thepresent invention.

FIG. 5C shows a perspective view of a treatment pattern on the surfacein accordance with the principals of present invention.

FIG. 6A illustrates the beam conversion system in two differentdistances from the surface.

FIG. 6B shows a cross section of the optical head constructed accordingto the principles of the present invention.

FIG. 7A shows a cross section of another embodiment of the beamconversion system incorporating the principles of the invention.

FIG. 7B illustrates a perspective view of another embodiment of the beamconversion system incorporating the principles of the invention.

FIG. 8A illustrates a combination of schematic and perspective view ofanother embodiment beam conversion system incorporating the principlesof the invention.

FIG. 8B illustrates a combination of schematic and perspective view ofstill another embodiment of the beam conversion system incorporating theprinciples of the invention.

FIG. 9 illustrates a schematic view of a dual wavelength laser sourceincorporating the principles of the invention.

FIG. 10A shows a cross section of another embodiment of the beamconversion system incorporating the principles of the invention.

FIG. 10B shows a cross section of yet another embodiment of the beamconversion system incorporating the principles of the invention.

FIG. 10C shows a cross section of one embodiment beam conversion systemincorporating the principles of the invention applied for hairtreatment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Reference is now made to FIGS. 1A to 1C, which are schematicillustrations of preferred embodiments of an apparatus 11 for practicingthe present invention. In FIG. 1A is shown the apparatus 11 including acontrollable radiation unit 14, a delivery system 13 and a treatmenthead 12. A radiation beam, preferably generated by the radiation unit 14is directed to a target region via the delivery system 13 and thetreatment head 12.

The radiation beam preferably comprises chromatic or monochromatic lightsuch as laser emission. Preferably, the delivery system 13 includes anoptical waveguide through which the radiation beam may travel to thetreatment head 12. The treatment head 12 includes at least one beamconversion system (not shown in FIG. 1A) that receives the radiationbeam, transforms the beam and directs a transformed beam to a treatmentarea. In one embodiment the treatment area is the subject's skin whilethe treatment head 12 is a handpiece held by the operator as illustratedin FIG. 1B.

FIG. 1C illustrates a schematic block diagram of a preferred embodimentof the apparatus. The apparatus preferably includes a radiation source16 for producing the radiation beam, a controllable beam converter orbeam conversion system 17 at least one of which is preferably includedin the treatment head 12 of FIGS. 1A and 1B, to direct the radiationbeam to the target 18, and a control system 19 that is preferablyincluded in radiation unit 14 of FIG. 1A for controlling the radiationsource and the beam conversion system. In another embodiment of presentinvention, the control system 19 is included in the treatment head 12.In yet another embodiment the radiation source 16 is included in thetreatment head 12.

The radiation source 16 can preferably be a laser source, which maygenerate a beam of pulsed or gated CW laser radiation of at least onewavelength. In another embodiment, the radiation source 16 generates alaser beam with a plurality of wavelengths. In another embodiment, theradiation source 16 generates incoherent radiation.

Reference is now made to FIG. 2A, which illustrates an applied inputradiation beam 86, of a predetermined diameter and a predeterminedinitial fluence F1, entering the beam conversion system 17. The beamconversion system 17 spreads out the radiation beam 86 into a number ofbeams, schematically, represented in FIG. 2A by two beams 41 and 41′,though it is to be understood that the number of beams will preferablybe many more, or even a continuum of beams fanned out around thecircumference. The beam conversion system 17 then redirects the beams 41and 41′ inwardly towards the surface 26 of the tissue, thus producing,on the surface 26, a spot in a shape of a disk 52, or segments of adisc, having a total area which is larger than the cross section area ofthe input beam 86. Therefore, the energy fluence F2 on the surface 26 islower than the input beam fluence F1.

The beams 41 and 41′ are directed to cross each other at a predetermineddepth below the tissue surface 26, to produce an overlap volume definedas target volume 46. The combined fluence F3 at the target volume 46 ishigher than the average energy fluence F2 on the surface. The fluence F3can be made less than, equal to, or greater than the input fluence F1,according to whether the beam conversion system applies any convergenceor divergence to the treatment beams 41 and 41′, and whether the inputbeam 86 itself is a collimated beam or a divergent or convergent beam.

The beam conversion system 17 thus delivers a therapeutic dose ofradiation to the target volume 46 while delivering a reduced dose ofradiation to overlying and surrounding tissues. The beam conversionsystem 17 can be moved around to treat a plurality of target volumes tocover the desired treatment area. For clarity, the term “therapeuticdose” is understood to mean the amount of energy necessary to thermallyaffect the targeted region to elicit the therapeutic effect required ina specific application.

According to one preferred embodiment, the beam conversion system 17provides the spread of the input beam 86 by reducing the radiationexposure time of the surface while sustaining the radiation exposuretime of the target volume. This is preferably realized by causing theoutput beam from the beam converter to rotate around the axis of theinput beam, thus exposing the target volume during the entire energyexcitation period, while exposing the surface to radiation only during afraction of the energy excitation period. The beam rotation period maypreferably be made equal to the energy excitation period, or shorter.

Reference is now made to FIG. 2B which schematically illustrates onepreferred embodiment of the beam conversion system 17 including a pairof mirrors 24, 25 and a rotator 21, controlled by the control system 19of FIG. 1C. The mirror 24 is rotated about an axis 27 by a rotator 21,such as an electric motor. The point of intersection of the mirror andthe rotation axis is a distance A from the surface 26. The mirror ismounted in such position that the normal 28 to the surface of the mirror24 lies at an angle 35 to the rotation axis 27. The rotation axis 27 ispreferably perpendicular to the surface 26. The second mirror 25, isalso connected to the rotation axis turned by the rotator 21, and isarranged at a distance C from the axis 27 in a position facing themirror 24, such that the normal 30 to the surface of the mirror 25 liesat an angle 34 to the normal to surface 26 (and the axis 27).Preferably, the normal 30 lies in the plane defined by the rotation axis27 and the normal 28.

During an excitation mode, a preferably collimated beam, a center ofwhich is defined by vector 22, propagates from the radiation source 16of FIG. 1C, in a direction generally aligned with the rotation axis 27,impinging on the mirror 24 at an angle 35 to the normal 28 to produce areflected beam, a center of which is defined by a vector 29, whichimpinges on the mirror 25 at an angle 36 to the normal 30 to produce areflected beam, a center of which is defined by a vector 31. The mutualgeometrical arrangement of the mirrors is such that the reflected beamimpinges the surface 26 at an angle of incidence and is directed towardsthe target area below the surface, and generally on the axis 27.

As the rotator 21 rotates the mirrors 24 and 25 at an angular velocity Wabout the symmetry axis 27, the vector 31 traces a circle of radius R onthe surface 26 around the symmetry axis 27. In one embodiment a sensor(not shown), connected to the control unit 19, is provided fordetermining the speed of rotation of the beam conversion system 17 andfor determining the location of the light beam impinging on the surface26.

Angle 37 is the angle of incidence between the vector 31 and the normalto the surface 26. A refracted beam, represented by vector 32,penetrates the tissue with a refraction angle 38.

According to Snell's Law: n1*sin(angle 37)=n2*sin(angle 38), where n1 isthe refraction index of the interposing medium, for example air, whilen2 is the refraction index of the tissue beneath the surface, forexample the cutaneous tissue. The index of refraction of the cutaneoustissue is approximately 1.5. Therefore, the angle 38 is smaller than theangle 37.

As the vector 31 traces a circle having radius R on the surface 26, thevector 32 rotates around the rotation axis 27 and crosses it at a targetpoint N, which is located at the depth of D below the surface 26.

The angles 35, 36, 34 and 37 and the distances A and C are all known bydesign. The refraction index for a variety of materials is known in theart. Therefore, the distance D can be calculated using simpletrigonometry laws.

Assuming for simplicity that angle 34 is 90 degrees, the distance D canbe calculated as follows:D=(2*C−A*tan(angle37))/(tan(angle38))The angle 38 is equal to arcsin((n1/n2)*sin(angle37). Therefore:D=(2*C−A*tan(angle37))/((tan(arcsin((n1/n2)*sin(angle37)))))

According to further preferred embodiments of the present invention, theradiation source 16 of FIG. 1C may be incorporated into the beamconversion system 17. Reference is now made to FIG. 3F schematicallyillustrating a beam conversion system 17 according to such a preferredembodiment of the present invention, which includes a radiation source20, such as a laser diode or the output end of the optical deliverysystem 13 of FIG. 1A, mounted on the rotator 21 instead of mirror 24 ofFIG. 2B. During an excitation mode, a beam propagates from the radiationsource 20, impinging on the mirror 25F. The rotator 21 rotates theradiation source 20 and the mirror 25 about the symmetry axis 27 totrace a generally circular path on the surface 26 around the symmetryaxis 27.

Reference is now made to FIG. 3G illustrating another such preferredembodiment whereby at least one radiation source 20 is connected to therotator 21 instead of mirror 25 of FIG. 2B. The rotator 21 rotates theradiation source 20 to trace a generally circular path on the surface 26around the symmetry axis 27.

In any of the embodiments of FIGS. 3F and 3G, the source 20 couldpreferably be the output end of a fiber optical beam delivery system.

Reference is now made to FIG. 4A which illustrates penetration of anincidence laser beam 41 into the surface 26. In a preferred embodimentthe surface 26 is surface of the skin that includes a layer of epidermis43 and an underlying dermis 44. The beam 41 having a center representedby the vector 31 traces a circle having radius R on the surface 26. Dueto scattering effect, a refracted beam 42, a center of which isrepresented by vector 32 is divergent. The divergence angle generallydepends on tissue optical properties and is inversely related to thewavelength. The center of the beam 42 crosses the axis 27 at targetpoint N located at a depth D below the surface 26. If during therotation of the beam conversion system 17 of FIG. 1C, the radiationsource 16 of FIG. 1C emits energy, the target volume 46 is continuouslyexposed to radiation. The beam 42 normally has a Gaussian powerdistribution with a maximum energy at the center of the beam. The targetpoint N receives maximum thermal dose and therefore defines a thermalcenter of the target volume 46.

The extent of thermal damage to the tissue is directly proportional topower density or irradiance and the exposure time. If the exposure timeis shorter than the target's thermal relaxation time (defined as thetime required for a target to cool from the temperature achievedimmediately after laser irradiation to half that temperature), heat willnot be able to diffuse out. This allows the thermal damage to be limitedto the target volume 46. The optimal exposure time may vary in differentapplications.

Referring now to FIG. 4B, in one specific embodiment, to counteract theeffects of scattering, the beam 41 of FIG. 4A is made convergent. Itmust be emphasized that the convergence is normally directed to a regionlocated far beyond the treatment zone. To achieve that, in oneembodiment, the radiation beam 86 is made convergent using techniquesknown in the art, prior to entering the beam conversion system 17. Suchconvergence can be symmetrical or in one specific dimension as could beachieved using cylindrical lenses known in the art.

In another embodiment the convergence of beam 41 can be achieved bymodifying the shapes of the reflecting surfaces of the mirror 24 and themirror 25 of FIG. 2B. This embodiment allows making the beam convergentin two planes separately, thus manipulating the cross sectional geometryof the beam 41, thereby controlling the cross-sectional powerdistribution of the beam 41. For example, the cross section of beam 41can be made elliptical. Such manipulation can assist in producing targetvolumes 46 of different shapes.

Reference is now made to FIG. 3A which schematically illustrates aperspective view of one embodiment in which the convergence is made inthe plane parallel to surface 26. In this embodiment, the mirror 25consists of a cylindrical reflector 25A with an inner reflecting surface39. The reflector 25A rotates with the mirror 24.

In another preferred embodiment the inner reflecting surface 39 of thereflector 25B is a concave mirror as illustrated in the schematicillustration of FIG. 3B. The configuration shown in FIG. 3A providesconvergence of the beam in a plane generally parallel to the tissuesurface 26, while the configuration shown in FIG. 3B additionallyprovides convergence of the beam in a second plane, generallyperpendicular to the tissue surface 26. A similar effect can be achievedby modifying the shape of the reflecting surface of the mirror 24.

FIG. 3C illustrates a perspective view of another preferred embodimentin which a cylindrical reflector 24A produces convergence in a planeparallel to surface 26, while the cylindrical reflector 25C producesconvergence in a plane perpendicular to surface 26. Therefore, theconvergence can be produced independently both in the plane parallel tothe surface 26 and in the plane perpendicular to the surface 26.

Reference is now made to FIG. 3D which schematically illustrates aperspective view of one preferred embodiment in which the convergence ismade in a plane parallel to the tissue surface 26. In this embodiment,the mirror 25 of FIG. 2B consists of a right circular conical frustrumreflector 25D with an inner reflecting surface 39. The symmetry axis ofthe reflector 25D is aligned with the symmetry axis 27. In oneembodiment, the reflector 25D rotates with the mirror 24, while in analternative embodiment the reflector 25D is static.

Reference is now made to FIG. 3E which schematically illustrates aperspective view of another preferred embodiment in which the innerreflecting surface 39 of the conical frustrum reflector 25E is a concavemirror having its curvature in the same plane as that of mirror 25B ofFIG. 3B. The configuration shown in FIG. 3D provides convergence of thebeam in plane generally parallel to the tissue surface 26, while theconfiguration shown in FIG. 3E additionally provides convergence of thebeam in a second plane, generally perpendicular to the tissue surface26. In both embodiments shown in FIGS. 3D and 3E, the convergence of thebeam in a plane generally parallel to the tissue surface 26 produces afocal point, located outside the tissue. However, the redivergence ofthis focused beam before it impinges the tissue surface ensures that thedesired spreading effect is maintained.

In a further preferred embodiment, the beam 41 is generally collimated,while in another embodiment it is substituted by a convergent beam 47 asillustrated in FIG. 4B. The refracted beam 48 is convergent tocompensate for the scattering effect of the tissue, or in anotherembodiment the convergence can be more severe, resulting in a smallerand more intense target volume 46. The convergence of beam can beachieved by any of the preferred configurations described above.

The shape, size, power intensity distribution and depth below surface 26of the target volume 46 depends on the diameter of the laser beam, across section power distribution of the beam, the refraction angle 38and other geometric parameters as shown above. Some of those parameterscan be dynamically manipulated using the principles of presentinvention. Moreover, those parameters can be altered during duration ofa single energy pulse or during a single rotation cycle of the rotatingelements of the beam conversion system 17. For example, the target pointN can be altered, thus altering the depth D of target volume 46 during asingle rotation cycle. This can be accomplished if, for example, insteadof the circular conical frustrum 25D in FIG. 3D a conical frustrum withelliptical cross section is applied. In such a case, the target point Nwill sweep along the axis 27, between two vertical points. The distancebetween those points is determined by the ratio between the semi-majorand semi-minor axis of the ellipse. In another example, the targetvolume 46 can be made wider and shorter by making the beam 41 convergentin plan parallel to surface 26. This can be useful for applicationsrequiring targeting relatively shallow layers of the tissue.

To control the depth below the surface 26 of the target volume 46, thedistance D and the radius R can be dynamically adjusted as illustratedin FIG. 6A. When the beam conversion system 17 is positioned at a firstdistance from the surface 26, the target point N1 is at a depth D1. Whenthe beam conversion system 17 is positioned at an alternate distancefrom the surface 26, the target point N2 moves to a depth D2. The beamconversion system 17 is repositioned vertically using any linearpositioning device known in the art, controlled by the control unit 19.

In another embodiment of present invention, with reference to FIG. 2Band FIG. 4A, the radius R and the distance D are adjusted by changingone or more of angles 34, 35 or the distance between the mirrors 24 and25 or the distance between each of the mirrors 24 and 25, and thesurface 26.

Reference is now made to FIG. 6B which schematically illustrates oneembodiment of the beam conversion system 17, constructed in accordancewith the principles of the present invention. The beam conversion system17 includes a cylindrical structure 61 containing both mirrors 24 and25. The mirrors may be separate elements, available from Laser BeamProducts (Cambridge UK), attached to the structure 61 or they may bepolished surfaces of the structure 61. A rotation means in this case isa controllable dual motion activator 64 that has both rotary and linearmotion, such as is supplied by Haydon Switch & Instrument, of Waterbury,Conn. The beam conversion system 17 also includes an externalcylindrical enclosure 62 to which the activator 64 is mechanicallyattached. The enclosure 62 also includes an opening 63 for the laserbeam to enter the beam conversion system and an opening 65 through whicha redirected beam, represented by the vector 32, exits the beamconversion system. The rotation means provides both the rotation of thestructure 61 and its vertical movement, controllable by control system19 of FIG. 1C.

As explained above, the location of the target point N along the axis 27as specified by the distance D is dynamically adjustable. Therefore, bycontrolling the amount of transmitted energy and the location of thetarget point N, a target zone of a desired form and size can be created.

Reference is now made to FIG. 5A which schematically illustrates aperspective view of an elliptical spot 51 produced by the projection ofthe beam 41 on the surface 26. As the beam conversion system rotates, itprojects the elliptical spot 51 on the surface 26 in a form of a disk52. The area of the disk 52 is significantly larger than the area of theelliptical spot 51. An average exposure time of any single point on thedisk 52 during one rotation cycle is therefore significantly smallerthan the period of the cycle. The thermal effect of light energy on thesurface 26 depends on the energy fluence or power density of the lightbeam multiplied by the exposure time to the light beam. For any givenpower density, the reduced exposure time results in significantly lessfluence and consequently less damage to the surface 26 of the tissue. Ifthe tissue treated is the skin, less damage is caused to the superficiallayers of the skin such as the epidermis and papillary layer of thedermis.

The following numerical example can be used to illustrate the reducedexposure to the surface of the tissue. Referring to FIG. 4A, andassuming that the beam 41 is delivered in pulses of duration equal toone rotation period of the beam 41, that the angle 37 is 45 degrees, andthe refraction index of the skin is 1.44, the refraction angle 38 isapproximately 29.4 degrees. If the diameter of the beam 41 is 0.8 mm andthe required penetration depth D is 2 mm, the area of the disk 52 is6.51 square mm while the area of the ellipse 51 is 0.58 square mm. Theratio between the areas of the ellipse 51 and the disk 52 isproportional to the average exposure time of the surface of the disk 52during the rotation cycle. It this example, this ratio is 0.089 whichmeans that the average exposure time of the surface of the disk 52 isapproximately 8.9 percent of the rotation period. Consequently, thesurface average fluence is 8.9 percent of the average fluence of thebeam 41 in an idle position.

Instead of generating the beam spreading effect by means of a rotatingstructure, the beam conversion system 17 can, according to otherpreferred embodiments of the present invention, provide the spread ofthe input radiation beam 86 statically by increasing the radiationexposure area at the surface while maintaining the radiation exposurearea of the target volume. This is realized by splitting the radiationbeam into a plurality of beams, redirecting the plurality of beams atpredetermined incident angles inwards towards the surface, and pointingtowards the symmetry axis which is generally normal to the surface, suchthat the plurality of beams are reassembled into the target volume at apredetermined depth.

Reference is now made to FIG. 7A which schematically illustrates a crosssection of such a preferred embodiment of the beam conversion system 17that includes a right angular cone 84 that has a symmetry axis 82,generally normal to the surface 26 and a reflecting surface 81. Theangle between the axis 82 and a normal 80 to the surface 81 is an angle85. The element 84 does not have to be a cone, which reflects a fannedout beam in all directions. It could be a facetted mirror, whichreflects a number of discrete radial beams. Either of the reflectors canbe in a variety of geometric forms and configurations suitable for bothcollimated and convergent beams.

The beam conversion system 17 further includes a right circular conicalfrustrum reflector 83 with an inner reflecting surface 99 and a symmetryaxis preferably aligned with the symmetry axis 82. The angle between thenormal to the surface 26 and the normal to the reflecting surface 99 isan angle 94.

The distance between the symmetry axis 82 and the reflecting surface 99is C1. The distance between the top of the cone 84 and the surface 26 isA1.

During an excitation mode, a laser beam 86, a center of which is definedby a vector that is aligned with the symmetry axis 82, propagates fromthe radiation source 16 of FIG. 1C. The beam 86, impinging on thereflecting surface 81 at an angle 85 to the normal 80, will produce aplurality of reflected beams spreading outwards the symmetry axis 82.These reflected beams are schematically represented by a beam 88, ageometry center of which is defined by a vector 89. The reflected beamsrepresented by the beam 88 impinging on the reflecting surface 99 at anangle 96 to a normal 90 will produce a plurality of reflected beams. Theplurality of reflected beams, one of which is schematically illustratedby a beam 91, a center of which is defined by a vector 87, directedinwards the symmetry axis 82. The geometry center of the beam 91 definedby the vector 87 does not necessarily represent the maximum crosssectional energy density of beam 91.

The plurality of beams, one of which is schematically illustrated by thebeam 91, a center of which is illustrated by the vector 87 creates acircle of radius R on the surface 26 around the symmetry axis 82. Angle97 is an angle of incidence between the vector 87 and the normal to thesurface 26.

The plurality of beams one of which is schematically illustrated by thebeam 91, penetrate the surface 26, to create a plurality of refractedbeams, one of which is schematically illustrated by a beam 92, a centerof which is defined by a vector 93. An angle between the vector 93 andthe normal to the surface 26 is a refraction angle 98. Due to scatteringeffect, the refracted beam 92 may be moderately divergent.

Similar to the embodiments illustrated in FIG. 2B and described above,the geometric centers of the plurality of beams, one of whichschematically illustrated by a beam 92, cross each other at a targetvolume 49. A geometric center of volume 49 is represented by point K,which is located at the depth of D below the surface 26. The angles 85,96, 94 and 97 and the distances A1 and C1 are all known by design. Therefraction index for variety of materials is known in the art.Therefore, the distance D can be calculated using simple trigonometrylaws. In a preferred embodiment of the present invention, the radius Rand the distance D can be dynamically adjustable by for examplecontrolling the distance A1 or the distance between the beam conversionsystem 17 and the surface 26.

FIG. 7B exemplifies one such system. FIG. 7B illustrates a perspectiveview of the beam conversion system 17 of FIG. 7A that illustrates aspecific embodiment in which the surface 83 is a cylinder. The angle 94between the symmetry axis 82 and the reflective surface 99 is 90degrees.

The shape and the size of the target volume 49 mostly depend on thediameter of the laser beam, the cross section power distribution of thebeam, the refraction angle 98 and the scattering effect of the tissue.Due to geometric considerations, the thermal exposure will besymmetrically distributed around the symmetry axis 82. However, in thisembodiment, the point K will not necessarily receive maximum thermaldose.

The shape and the size of the target volume 49 as well as the energydistribution are controllable to fit the desired application.

It should be emphasized that in these preferred embodiments, the beam 86is generally collimated. Moreover, the beam conversion system does notfocus the beam 86 at any point, thus the fluence at any point is nohigher then the fluence of the beam 86.

According to another preferred embodiment, to counteract the effects oftissue scattering, the beam 91 is made convergent. To achieve this, inone preferred embodiment, the radiation beam 86 is made convergent usingtechniques known in the art, prior to entering the beam conversionsystem 17. In another embodiment, beam convergence on the surface 26 canbe achieved by modifying the shape of the reflecting surface 81 of thecone 84 and the reflecting surface 99 of the frustrum 83 of FIG. 7A.

For example, similarly to the embodiment illustrated in FIG. 3A theconvergence of the beam 91 is made in the plane generally perpendicularto the surface 26 by making the surface 99 of the frustrum 83 of FIG. 7Aa concave reflector having reflective surface similar to the reflectivesurface 39 illustrated in FIG. 3E. Such manipulation can assist inproducing a target volume 49 of a desired shape.

In another preferred embodiment, instead of the right angular cone 84, aspherical cap is used. Accordingly, instead of the right circularconical frustrum reflector 83, a second spherical cap with an innerreflecting surface and a symmetry axis preferably aligned with thesymmetry axis 82 is used. It should be appreciated that presentinvention can be practiced using reflectors in a variety of geometricforms and configurations suitable for both collimated and convergentbeams.

The shape, size, power intensity distribution and depth below thesurface 26 of the target volume 49 is mostly depend on the diameter ofthe laser beam, the cross section power distribution of the beam, therefraction angle 98 and other geometric parameters as shown above. Someof those parameters can be dynamically manipulated using furtherembodiments of the present invention. Moreover, some of those parameterscan be altered during the duration of a single energy pulse. Forexample, the distance D of the target point K can be altered thusaltering the depth of target volume 49 during a single energy pulse.This can be accomplished, for example, if instead of circular conicalfrustrum 83 in FIGS. 7A-B, a conical frustrum with elliptical crosssection is used. In such a case, the target point K will be sweepingalong the axis 82, between two vertical points. The distance betweenthose points is determined by the ratio between the semi-major andsemi-minor axis of the ellipse.

To control the depth below surface 26 of the target volume 46, thedistance D the radius R can be dynamically adjusted as illustrated inFIG. 6A and as explained hereinabove.

In another embodiment of present invention, with reference to FIG. 7A,the radius R and the distance D are adjustable by changing one or moreof angles 85, 94 or the distances C1 and A1.

Referring now to FIG. 7B, the plurality of reflected beams, one of whichis schematically illustrated by the beam 91 projecting illumination inthe form of the disk 52 on the surface 26. The surface of the disk 52 issignificantly larger than the surface of the cross section of the beam86. Therefore, for any given exposure time, the power density at anyspecific point on the surface of the disk 52 is significantly lower thanthe power density of the beam 86. The reduced power density results insignificantly less damage to the superficial layers of the tissue. Ifthe tissue treated is the skin, less damage is caused to the superficiallayers of the skin such as the epidermis and papillary layer of thedermis.

Reference is now made to FIG. 8A, which schematically illustratesanother preferred embodiment of the beam conversion system 17. Inaddition to the beam conversion system 17 described above as illustratedin FIG. 7A which includes a right angular cone 84 and a right circularconical frustrum reflector 83, this embodiment also includes a scanningsystem 100. The scanning system 100 directs the beam 103, propagatingfrom radiation source 16 of FIG. 1C. in a circular, spiral or anydesired pattern around the axis 82. This can preferably be accomplishedusing techniques known in the art, for example applying a galvanometricscanner with mirrors 101 and 102 operated at 90 degrees out of phase.Suitable galvanometers can be supplied by GSI Lumonics, of Moorpark,Calif.

During the excitation mode, the laser beam 104 propagates from thescanning system 100 with an angle 105 between the symmetry axis 82 and acenter of the beam 105, which is defined by vector 106. The beam 104,after being reflected from the reflecting surface 81 at the angle 85A tothe normal 80, is represented by a beam 88A, a center of which isdefined by a vector 89A, which thereafter is reflected from thereflecting surface 99A at an angle 96A to the normal 90 to surface 99,schematically illustrated by a beam 91A, a center of which is defined bya vector 87A.

As will be shown in the following description, this embodiment combinesthe functionalities of the previously described embodiments usingrespectively time-spread and spatially-spread beam conversionconfigurations. If the scanning system 100 is idle in a position thatdirects the beam 103 such that the vector 106 is aligned with the axis82 (the angle 105 is zero), the beam conversion system 17 will behave insimilar manner to the embodiment described in FIG. 7A. On the otherhand, if the scanning system 100 rotates the beam 103 in a circular orspiral motion pattern around the axis 82, the result produced by thebeam conversion system is similar to that described in the embodimentillustrated in FIG. 2B, having a rotating element.

As the beam 104 rotates in a circular pattern around the axis 82, thebeam 91A, a center of which is illustrated by vector 87A, creates acircle of radius R on the surface 26 around the symmetry axis 82. Theangle 97A is the angle of incidence between the vector 87A and thenormal to the surface 26.

The beam 91A penetrates the surface 26, to create a refracted beam 92A,a center of which is defined by a vector 93A. An angle between thevector 93A and the normal to the surface 26 is a refraction angle 98.Due to scattering effect, the refracted beam 92 may be moderatelydivergent.

The center of beam 92 crosses the symmetry axis 82 at a target point N,which is located at the depth of D below the surface 26. The targetpoint N will be continuously exposed to radiation and therefore willreceive a maximum thermal doze. The target point N therefore defines thethermal center of the target volume 46. The shape and the size of thetarget volume 46 mostly depend on the diameter of the laser beam, thecross section power distribution of the beam, the refraction angle 98Aand the scattering and absorption effect of the tissue. Due to geometricconsiderations, the thermal exposure will be symmetrically distributedaround the symmetry axis 82, while the maximum thermal energy willnormally be at target point N.

The angles 105, 85A, 96A, 94 and 97A and the distances A1 and C1 are allknown by design. The refraction index for variety of materials is knownin the art. Therefore, the distance D can be calculated using simpletrigonometry laws.

By varying the angle 105, we can manipulate the distance R and thedistance D. Alternatively, we can alter any of the: angle 94, distancesA1 or distance C1 in order to manipulate the distance R and the distanceD. Moreover, instead of causing the beam 105 rotate in a circularpattern around the axis 82, the system 100 is capable of producing avariety of geometric forms around the axis 82. That may includeelliptical or even rectangular forms or discrete steps instead ofcontinuous motion. All those manipulations allow producing the targetvolumes 46 of a various shapes, sizes, depths and energy distributionrequired for a specific application. These manipulations can beperformed either between treatments, or even during the course of asingle excitation pulse.

An example of an additional preferred embodiment, utilizing the scanningsystem 100, but without the right angular cone 84, is illustrated inFIG. 8B.

It should be appreciated that these embodiments of the present inventioncan also be practiced using reflectors in a variety of geometric formsand configurations.

Another aspect of present invention is the simultaneous thermaltreatment of multiple confine target volumes, preferably with differentwavelengths and preferably with different pulse durations. Suchconfigurations utilize a radiation source that can produce a beam withmultiple wavelengths. An example of such a laser is a dual wavelengthNd:YAG laser. In one embodiment of the present invention, the radiationsource 16 of FIG. 1C is a multiple wavelength laser 110, as depicted inFIG. 9. Flash pumped Nd:YAG lasers can be operated at both 1064 and 1320nm. By coating the flat ends of a crystal 111 of typical size of 150 mmlength and 8 mm diameter with a 1064 nm partial reflector 114 and 1320nm partial reflector 119, as well as by using a 1064 total reflector 113and 1320 nm total reflector 112, the laser can simultaneously emit a1064 nm beam 116 and a 1320 nm beam 115. A beam combiner 117 enables theemission of a combined 1064 and 1320 nm beam 118. The pulse duration ofthe beam depends on the duration of the pumping flash-lamp and istypically between 1 millisecond to 300 milliseconds. Typical energydensity at each wavelength may be 10-3000 Joules/cm2. A dual wavelengthNd:YAG laser may also be produced by the utilization of two rods, eachrod coated for different wavelengths.

In another preferred embodiment of the present invention, a very highintensity array of diode lasers at different wavelengths (such as 755 nmand 810 nm) may be used. The lasers are operated with different pulsedurations by varying the current pulse duration generated by the powersupply.

Reference is now made to FIG. 10A which shows one preferred method ofimplementing this dual wavelength embodiment of the present invention.During the excitation mode, a generally collimated, dual wavelengthlaser beam 118, such as one produced by multi-spectral laser 110, asdepicted in FIG. 9, hits a mirror 122 from which it is directed to areflective optical grating 123, which separates the two wavelengths andreflects the first beam 124 having first wavelength at first dispersionangle and the second beam 125 having a second wavelength at a seconddispersion angle. By combining the mirror 122 and the optical grating123 into a rotating unit 126 that rotates around the rotation axis 27,two scanning beams are generated, which simultaneously treat the targetvolume 127 with the beam 124 of the first wavelength and the targetvolume 128 with the beam 125 of the second wavelength.

The confined target volume 127 and the confined target volume 128 arevertically separated and treated with separate wavelengths, optimizedfor the required application. The angular rotation speed of the rotatingunit 126 and the duration of the excitation time of the laser beam 118are optimized to treat the specific lesions. Separate treatment timescan be provided to each volume by exposure of each volume to a pulsewith different duration. For example, at a speed of 6000 revolutions perminute (corresponding to a full circle scanning time of 10 ms), thetarget volume 127 could be treated with a 10 ms pulse, which correspondsto one rotation time, while the target volume 128 could be treated witha 50 ms pulse, which corresponds to 5 full rotations.

Reference is now made to FIG. 10B which shows a schematic representationof another preferred embodiment of the present invention, which providesadditional temporal discrimination by excitation of dual wavelengthlaser beam 118 emitted by the laser at different wavelengths withdifferent pulse durations. This is achieved, for example, byelectronically controlling an intracavity laser shutter. A dichroicmirror 132 reflects beam 133 having wavelength lambda 1 and transmitsbeam 134 having wavelength lambda 2. The beam 133 is reflected from themirror 135 and becomes beam 143 which is targeted to treat the confinedvolume target 146. The beam 134, reflected from mirror 137, becomes beam144 which reflects from mirror 138 and is targeted to treat the confinedvolume target 147.

By combining the pair of mirrors 132 and 135 into a rotating unit 140and the pair of mirrors 137 and 138 into a rotating unit 141, and byrotating the units 140 and 141 around the rotation axis 27, two scanningbeams are generated, which simultaneously treat two target volumes underthe surface 26. The target volume 146 is targeted by beam 143 while thetarget volume 147 is targeted by beam 145.

According to another preferred embodiment, the beam 118 is a singlewavelength beam, such as 1064 nm, and the dichroic mirror 132 issubstituted with a partial beam splitter which reflects part of theenergy while the rest of the energy passes through. In such a case,target volumes 146 and 147 can be treated simultaneously with eachreceiving a predetermined optimal amount of energy.

An electronic angular position control of the mirrors 132, 135, 137 and138 enables the variation of the depth of each of the treated volumes.It is possible to provide an electronically controlled shutter insidethe cavity, thereby further controlling the temporal emissions of thebeams, which hit the vertically separated target volumes.

In another embodiment, the dual wavelength laser beam is applied to thebeam conversion system of any of the FIGS. 7A, 7B, 8A and 8B in whichthe reflecting surface 99 is replaced by a reflective optical grating123, which separates the two wavelengths and allows treating twoseparate target volumes simultaneously.

For the purpose of this disclosure, the “target volume” is understood tomean a single volume that receives the thermal dose withoutrepositioning target point N (or target point K in some embodiments).The “target zone” is understood to mean a plurality of target volumesall sharing a common axis 27 (or axis 82 is some drawings). The“treatment area” is understood to mean the region of the tissue thatneeds to be treated, preferably by creating a plurality of target zones.

In accordance with the principal of present invention and it differentembodiments, after the a desired thermal effect is achieved in arequired target zone, the target point N (or K in some embodiments) canbe repositioned to a new treatment location on the surface of the tissueto produce new target volumes that form a new target zone. This couldpreferably be achieved by horizontal and angular (changing the anglebetween the axis and the normal to surface 26) repositioning of the axis27 (or axis 82 is some embodiments). Therefore, by multiplerepositioning of the axis 27 in discrete or continuous manner, anydesired, treatment paths on the surface 26 can be created, covering thetreatment area to suit a specific application.

In another preferred embodiment, the reposition of axis 27 is achievedby repositioning the beam conversion system, which could be accomplishedmanually by repositioning the treatment head.

In another embodiment, instead of manual repositioning of the treatmenthead, a mechanical two-dimensional positioning system known in art suchas the one from Arrick Robotics Inc., can be included in the treatmenthead for scanning the treatment area.

In another embodiment, a plurality of treatment heads are provided in aform of two-dimensional matrix for treating larger treatment areas insimultaneous or in sequential manner.

FIG. 5B illustrates another preferred embodiment at which instead ofproducing the disk 52 of FIG. 5A in a continuous motion, the spot 51 isscanned over the surface 26 in a series of discrete steps. The beam 41,which is represented by vector 31, is initially positioned to produce aspot 51. Thereafter, the beam 41 is repositioned to produce a pluralityof spots schematically exemplified by spots 53, 54, 55, 56 and 57 andconsequently produce the target volume 46. In one embodiment, in orderto reduce the accumulated heat in the superficial layer of the skin andto minimize the pain sensation, the locations 51, 53, 54, 55, 56 and 57are arranged to be not adjacent to each other.

FIG. 5C illustrates another method of use, in which instead of producingthe treatment area in a continuous motion, the surface 26 is scanned ina series of discrete steps. The beam conversion system 17 is initiallypositioned to produce the disk 52A. Thereafter, the beam conversionsystem 17 is repositioned to produce a plurality of disks schematicallyexemplified by disks 528, 52C, 52D, 52E and 52F and consequently producethe target volumes (not shown) under each of those disks using theprinciples of present invention and exemplified earlier.

In one embodiment, in order to reduce the accumulated heat in thesuperficial layer of the skin and to minimize the pain sensation, thelocations 51A, 52B, 52C, 52D, 52E and 52F are arranged to be notadjacent to each other.

Any of the above embodiments of the present invention can be performedusing sources of energy such as radiofrequency (RF), microwave,ultrasound or other electromagnetic radiation applied in combinationwith the light energy. One particular advantage of the present inventionwhen operated in combination with the RF, is in the manipulation of theRF electrical conductivity of the tissue by optical preheating of aconfined target volume under the tissue surface.

The present invention can be practiced alone or with improvements knownin the art, such as optical tracking system for controlling thetreatment location, application of gel to the skin in order to reducelight scattering resulted from irregularities in the skin, use of anaiming beam for marking the treatment area, cooling before and/or duringtreatment, and imaging devices for visualization of the treatmenttarget.

Applications

The present invention can be utilized in a variety of medical andaesthetic applications. Following are several examples that illustratesome of those applications.

EXAMPLE 1 An Application for Removing Wrinkles

Removing wrinkles in accordance with present invention includesdelivering a beam of laser or incoherent radiation capable of causingsufficient thermal injury in the dermal region of the skin. The thermalinjury elicits a healing response, which causes the skin to remodelitself, resulting in substantially less wrinkled skin. In particular,thermal injury causes partial denaturation of the collagen fibers in thetargeted dermal region of skin. In one embodiment of present invention,the radiation directed to partially denature collagen in the dermiswhile reducing the thermal damage to the epidermis and upper layers ofthe dermis. As a result, a subject treated using the method of thepresent invention will have lessened wrinkles without damage to theepidermis.

Light penetration depth is a function of wavelength of the light source.A wavelength in the range of 800 to 1900 nm is appropriate in order toachieve deep collagen heating. Preferably, the wavelength in the rangeof 570-800 nm is utilized for shallower collagen contraction.

The laser beam 86 (or beam 104 or beam 118 in various embodimentsdescribed herein) utilized for this application, preferably has afluence of between about 10 and 3000 joules/cm2. For example, a 1064 nmNd:YAG laser may be used, or a 1320 nm Nd:YAG laser or a 1500 nmNd:Glass laser or a 1450 nm diode laser.

The treatment volume should be at a skin depth larger than 100 microns,and can be varied in the range of 0.1 to 4 mm, preferably in the rangeof 0.1 to 1.2 mm.

For the treatment of a wrinkle in accordance with the present invention,the treatment head is positioned on subject's skin containing thewrinkle. The target point N is aimed at a depth of about 750 microns.The targeted dermal region is then irradiated with radiation pulsesexiting from the treatment head 12 until collagen in that regionreceives the desired thermal doze. To accomplish this, the collagen atthe selected depth in the targeted dermal region is preferably heated toa temperature in the range of about 50 to 70 degrees Celsius.

In another detailed embodiment, the region of skin including the wrinkleis stretched along the wrinkle before the beam of radiation is directedto the targeted dermal region below the wrinkle. Stretching the skinalong the wrinkle before irradiating the skin causes partialdenaturation of the collagen fibers across the wrinkle, while notdamaging the fibers along the wrinkle. Partially denaturing the fibersacross the wrinkle tightens the skin sufficiently to cause the wrinkleto disappear.

The present invention can also be utilized for shallow, ablativetreatment of the papillary dermis that is located at the depth ofapproximately 0.1-0.3 mm. By positioning the target volume at the depthof the papillary dermis, it is possible to ablate the papillary dermiswithout vaporizing the epidermis. A variety of wavelengths, preferablyin the infrared range, may be utilized for such purpose, includingwavelength produced by Erbium, Holmium or CO2 lasers. For example, a lowpower (10 watts) CO2 lasers may be utilized with a 1 ms pulse.

EXAMPLE 2 An Application for Treating Sagging and Folded Skin

Sagging and folded skin may be reduced by a mechanism that involvesshrinking collagen with heating. The thickness of the heated collageninfluences the efficiency of the treatment. In order to perform asuccessful treatment, light should penetrate through the epidermis andbe absorbed in deep layer of the dermis. Consequently, the treatmentvolume should be at a depth larger than 100 microns, and can be variedin the range of 0.1 to 4 mm. A wide range of wavelengths in the range of800 to 1900 nm is appropriate in order to achieve deep collagen heating.Generally, the radiation of laser beam 86 (or beam 104 or beam 118 invarious embodiments described herein) utilized for this application,preferably has a fluence of between about 10 and 3000 joules/cm2.

For example, a 1064 nm Nd:YAG laser may be used, or a 1320 nm Nd:YAGlaser or a 1500 nm Nd:Glass laser or a 1450 nm diode laser. It must beemphasized that laser beam with energy density as high as 500 joules/cm2in prior art lasers are normally creating severe adverse effects to theskin surface such as epidermal burn. However, by utilizing the presentinvention, the skin surface is not damaged because the fluence on theskin surface may be lower than 50 joules/cm2. In this application, thecollagen at the selected depth in the targeted dermal region ispreferably heated to a temperature in the range of about 65 to 85degrees Celsius.

EXAMPLE 3 An Application for Removing Unwanted Hair

In another embodiment, the present invention is utilized to removeunwanted hair. In accordance with one embodiment of present invention,the target volume could be positioned at a selected depth which can bevaried in the range of 0.1 to 4 mm along the hair follicle, therebyapplying thermal energy necessary for permanent or substantiallypermanent hair removal.

For example, by positioning the target volume generally concentric withthe bulge or the papilla maximum thermal energy is delivered into theareas believed to contain the cells responsible for hair growth, thuspromoting permanent or long-term hair removal. Unlike other methods, thepresent invention allows delivering sufficient amount of energy withoutdamaging the epidermis. Furthermore, the heating of each hair follicleis done directly and not through heat dissipation from the hair shaft asin some other methods.

Additionally, unlike other methods based solely on selectivephotothermolysis, the present invention allows using wavelengths, whichare less absorbed by the skin melanin, penetrate deeper and allowtreating darker skin patients. Furthermore, the substantially reducedfluence applied to epidermis in accordance with present invention mayallow treating even completely dark skin patients. Moreover, the melaninin the hair need not be targeted. However, if melanin is the targetedchromophor, only small amount of such chromophor is required to producethe desired thermal effect. As a result, gray and blond hair can betreated.

A wavelength in the range of 570 to 1100 nm is appropriate in order toreach the predetermined depth. For example, a 1064 nm Nd:YAG laser maybe used.

The laser beam 86 (or beam 104 or beam 118 in various embodimentsdescribed herein) utilized for this application, preferably has afluence of between about 10 and 3000 joules/cm2.

FIG. 10C illustrates an example of the beam conversion system of FIG.10A, applied for treatment of hair. The hair consists of the hair shaft150 that normally extends from the epidermis 43, a hair follicle 152 andhair root 153. The deepest and the thickest part of the hair is the bulb151, which is normally located in the dermis 44 up to approximately 4 mmbelow the surface 26.

Two particular zones, the first near the shaft base (papilla); and thesecond approximately a third of the way down the shaft, known as thebulge, are believed to contain the cells responsible for hair growth.Direct heat absorption into these zones and damage to them via heatingshould lead to permanent hair removal or at least substantially delayedregrowth.

In this embodiment, the confined target volume 127 and the confinedtarget volume 128 are positioned to simultaneously treat differentsubjacent depths of a hair follicle that are believed to be responsiblefor hair growth, with different optimal time durations. For example, thedeeper part of the hair is treated with longer wavelength of 810-1100 nmand longer pulse duration, typically 30-300 ms, while the shallow partof the hair can be treated with shorter wavelengths, typically 600-900nm and shorter pulses, typically 2-30 ms. Other embodiments of presentinvention can remove unwanted hair in similar manner.

EXAMPLE 4 An Application for Treating Varicose Veins

In another embodiment, the present invention is utilized to provide amethod and apparatus for treatment of vascular disorders.

In general, the larger is the penetration depth and the higher is theenergy delivered to the vessels wall, so more expanded is the heating ofvessels wall to cover a larger percentage of the interior and also moreof the vessel's walls. It is desirable therefore to use a high energylight for treating varicose veins, especially those that are larger anddeeper. One significant side effect of increasing the energy level is apotential damage to the epidermis. A significant advantage of thepresent invention is in reduction of such damage.

Preferably, the thermal dose is sufficient to cause total obstruction ofthe venous lumen.

Usually, the size and the depth of the targeted vessels dictate theeffective pulse duration and total fluence. The pulse duration shouldideally be closely matched to the thermal relaxation time of thevessels, which is a function of the vessels size. Generally, for thetreatment of the vessels such as varicose veins, a total effective pulsedurations of greater than a millisecond are desirable, with 5milliseconds to 100 milliseconds being preferred in the case of largervessels.

Over the course of the pulse duration, the fluence should be high enoughto raise the temperature of the walls of the vessel to a temperature atwhich their constituent proteins will denature. Preferably, atemperature of 70 degrees Celsius is an accepted target.

The laser beam 86 (or beam 104 or beam 118 in various embodimentsdescribed herein) utilized for this application, preferably has afluence of between about 10 and 3000 joules/cm2. For deep lying and/orlarger vessels the desirable wavelength range is the near-infrared. Forexample, a 1064 nm Nd:YAG laser, with 100 ms pulse duration, may beused.

LIST OF APPLICATIONS

In addition to several specific application described in details above,the present invention is utilized to provide a method and apparatus fortreating many dermatological disorders including but not limited towrinkles, stretch marks, vascular disorders, hair removal, treatment ofPFB, treatment of acne or chicken pox scars or other scars in the skin,treating cellulite, elimination of pigmented lesions and tattoos,treatment of psoriasis, skin resurfacing as well as non-ablativephotorejuvenation, treatment of various skin tumors. The presentinvention may also be used to treat intradermal parasites such as larvamigrans as well as to treat fungus nails and various other conditionswhich may exist in the patient's body at depths of less thanapproximately 4 mm.

Additional applications related to thermal shrinking of the collagenthat may include non-surgical treatment of aesthetic disorders relatedto sagging or folding skin such as mild breast ptosis, nasolabial folds,drooping jowls, eyelids, saggy arms, abdomen and thighs as well as otherbody sites.

The present invention is not limited to the treatment of dermatologicalproblems. The method is useful in many additional applications thatrequire treating deeper layers of the tissue while sparing the overlyingsuperficial layers. Therefore, in is still another specific embodiment,the present invention is utilized to provide a method and apparatus fortreatment of non-dermal tissues. That includes sub-surface ablation andcoagulation of tissue for example during open or laparoscopic surgery aswell as other minimally invasive procedures. The treatment head can beminiaturized to fit laparoscopic equipment or a catheter and to be usedfor a variety of medical conditions.

While the present invention has been particularly shown and describedwith reference to specific embodiments, it should be understood by thoseskilled in the art that various changes in form and detail may be madetherein without departing from the spirit and scope of the presentinvention as defined by the appended claims.

Accordingly, modifications such as those suggested above, but notlimited thereto, are to be considered within the scope of the presentinvention.

1. Apparatus for delivering radiation to a target volume (46) beneath askin surface, comprising: a radiation source (16) for inputting a beamof said radiation having an input energy fluence; and a beam conversionsystem (17) comprising: a rotator (21) having a rotation axis in opticalalignment with said beam and a first radiation directing element (24)arranged in optical communication with said radiation source comprisinga reflective element rigidly mounted on said rotator having a symmetryaxis (27), collinear with said rotation axis for rotating said inputbeam around said symmetry axis said first radiation directing elementadapted to direct said beam in a plurality of directions spaced aroundsaid symmetry axis, and a second radiation directing element (25)comprising a single reflective element mounted at a fixed distance fromsaid rotation axis facing said first radiation directing element forredirecting said directed beam through said surface radially inwardstowards said symmetry axis onto said at least one target volume (46)disposed on said symmetry axis beneath said skin surface, such that saidradiation is spread out in a rotational path on said surface, whereinsaid rotator is adapted to direct said beam in directions such that anygiven point of said target volume is exposed to said radiation duringthe entire energy excitation period of said beam, while any given pointof said rotational path on said surface is exposed to said radiationonly during portion of said enemy excitation period, and said firstradiation directing element (24A) has reflecting surface with curvaturein at most, one plane, and said second radiation directing element (25)has reflecting surface (39) with curvature in at most, one plane, andnone of said radiation impinging on said skin surface overlaps with saidsymmetry axis, and said energy fluence of said radiation at said targetvolume is higher than said energy fluence of said radiation at said skinsurface.
 2. The apparatus according to claim 1 wherein said secondradiation directing element is rigidly mounted on said rotator and isrigidly coupled to said first radiation directing element.
 3. Theapparatus according to claim 1 wherein said radiation has a spectralband between 300 nm and 11000 nm.
 4. The apparatus according to claim 1,said first radiation directing element and said second radiationdirecting element are selected such that said energy fluence of saidredirected beam is less than or equal to said energy fluence of saidinput beam.
 5. The apparatus according to claim 1, said first radiationdirecting element and said second radiation directing element areselected such that the focal point of such beam is located beyond saidtarget volume.
 6. The apparatus according to claim 1 wherein saidredirected radiation is in a collimated form.
 7. The apparatus accordingto claim 1 wherein said beam conversion system converges said radiationonto said target volume without the use of elements having opticalpower.
 8. The apparatus according to claim 1 wherein said secondradiation directing element converges said radiation onto said targetvolume without the use of elements having optical power.
 9. Theapparatus according to claim 1 wherein said period of said rotation isshorter than or equal to the duration of said energy excitation period.10. The apparatus according to claim 1 wherein said energy excitationperiod is a multiple of said period of said rotation.
 11. The apparatusaccording to claim 1 wherein said energy excitation period is from 1millisecond to 300 milliseconds.
 12. A method for delivering radiationbeneath a skin surface, comprising the steps of: providing a radiationsource for inputting a beam of said radiation having an input energyfluence; and providing a rotator having a rotation axis in opticalalignment with said beam; and providing a first radiation directingelement arranged in optical communication with said radiation sourcecomprising a reflective element rigidly mounted on said rotator having asymmetry axis, collinear with said rotation axis for rotating said inputbeam around said symmetry axis said first radiation directing elementadapted to direct said beam in a plurality of directions spaced aroundsaid symmetry axis; and providing a second radiation directing elementcomprising a single reflective element mounted at a fixed distance fromsaid rotation axis facing said first radiation directing element forredirecting said directed beam through said surface radially inwardstowards said symmetry axis onto said at least one target volume disposedon said symmetry axis beneath said skin surface, such that saidradiation is spread out in a rotational path on said surface, whereinany given point of said target volume is exposed to said radiationduring the entire energy excitation period of said beam, while any givenpoint of said rotational path on said surface is exposed to saidradiation only during portion of said energy excitation period, and saidfirst radiation directing element has reflecting surface with curvaturein at most, one plane, and said second radiation directing element hasreflecting surface with curvature in at most, one plane, and none ofsaid radiation impinging on said skin surface overlaps with saidsymmetry axis, and said energy fluence of said radiation at said targetvolume is higher than said energy fluence of said radiation at said skinsurface.
 13. A method according to claim 12 and further comprising thestep of providing a second reflective element rigidly mounted on saidrotator and rigidly coupled to said first radiation directing elementfor rotating said input radiation around said symmetry axis, such thatsaid radiation is spread out in a rotational path on said surface.
 14. Amethod according to claim 12 and further comprising the step ofproviding a first radiation directing element and a second radiationdirecting element for converging said radiation onto said target volumewithout the use of elements having optical power.
 15. A method accordingto claim 12 and further comprising the step of providing a firstradiation directing element and a second radiation directing elementwherein said radiation is non-focused at said target volume.
 16. Amethod according to claim 13 and wherein said rotated radiation is in agenerally collimated form.
 17. A method according to claim 12, andfurther comprising the step of providing a first radiation directingelement and a second radiation directing element wherein said energyfluence of said redirected beam is less than or equal to said energyfluence of said input beam.